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Structural Stability

Since structural collapse is second only to falls as a cause of fatalities in this industry, stability is essential to the successful erection of any steel structure, including single- story, multi-story, bridges, etc. This section of the standard outlines the work practices that will prevent collapse due to lack of stability. In addition, it addresses slipping/tripping hazards and certain kinds of fall hazards encountered when working on steel structures.

Structural Failure Leads to Worker Fatalities

Case Report:

A crew of steelworkers was connecting a steel beam to a steel column on the seventh level of an airport structure. The base of the column was secured to a sheer concrete wall by temporary welds to an embedded steel plate. When the crew encountered a problem connecting the beam to the column, a decision was made to pull the top of the column one inch to the north to facilitate the connection. The pull was performed by tensioning a guy wire, using a come-along, applying a fork at the column being connected, and using a sleeper. One worker was seated on the beam that was being connected, while another was standing at the base of the column, atop the concrete wall. When the force of the tensioning caused the temporary welds at the column base to fracture, the column collapsed, and the two workers fell to their death.

Structural Failure Leads to Worker Fatalities

Case Report:

A crew of steelworkers was connecting a steel beam to a steel column on the seventh level of an airport structure. The base of the column was secured to a sheer concrete wall by temporary welds to an embedded steel plate. When the crew encountered a problem connecting the beam to the column, a decision was made to pull the top of the column one inch to the north to facilitate the connection. The pull was performed by tensioning a guy wire, using a come-along, applying a fork at the column being connected, and using a sleeper. One worker was seated on the beam that was being connected, while another was standing at the base of the column, atop the concrete wall. When the force of the tensioning caused the temporary welds at the column base to fracture, the column collapsed, and the two workers fell to their death.

Permanent floors must be installed as the erection of structural members progresses, with no more than eight stories between the erection floor and the upper-most permanent floor. [29 CFR 1926.754(b)(1)]

Unfinished bolting or welding above the foundation (or the uppermost secured floor) is not permitted to exceed the lesser of [29 CFR 1926.754(b)(2)]:

Four floors

48 feet (14.6 m)

Exceptions are allowed where structural integrity is accounted for in the design.

Safety nets or a fully planked or decked floor must be maintained directly under any erection work being performed, within the lesser of [29 CFR 1926.754(b)(3)]:

To prevent tripping hazards, the following components must not be attached so as to project from the top flanges of beams, joists, or beam attachments until after the metal decking, or other walking/working surface, has been installed [29 CFR 1926.754(c)(1)]:

Exception: These may be factory installed if all workers, including
connectors and deckers, use fall protection at all times. [CPL2-1.34, Q&A 25 (PDF*)]

When shear connectors are used in construction of composite floors, roofs and bridge decks, they must be laid out and installed after the metal decking has been installed, so the metal decking serves as a working platform. [29 CFR 1926.754(c)(1)]

Shear connectors may not be installed from within a controlled decking zone (CDZ). [29 CFR 1926.760(c)(7)]

Workers will not be permitted to walk the top surface of any structural steel member installed after July 18, 2006 that has been coated with paint or similar material, unless all of the following are met:

The coating has achieved a minimum average slip resistance of .50 in laboratory tests.

The tests were based on the appropriate ASTM standard test method and conducted by a qualified laboratory (Appendix B to this subpart references appropriate ASTM standard test methods).

Documentation of the test results is available at the site and to the steel erector.

When deemed necessary by a competent person, plumbing-up equipment must be installed during the steel erection process to ensure the stability of the structure. [29 CFR 1926.754(d)(1)]

When plumbing-up equipment is used, it must be in place and properly installed before the structure is loaded with construction material such as loads of joists, bundles of decking, or bundles of bridging. [29 CFR 1926.754(d)(2)]

Plumbing-up equipment may be removed only with the approval of a competent person. [29 CFR 1926.754(d)(3)]

Metal decking bundles must be landed on framing members so that enough support is provided to allow the bundles to be unbanded without dislodging the bundles from the supports. [29 CFR 1926.754(e)(1)(iv)]

At the end of the shift or when environmental or jobsite conditions require, metal decking must be secured against displacement. [29 CFR 1926.754(e)(1)(v)]

Roof and Floor Holes and Openings:

Metal decking at roof and floor holes and openings must be installed as follows:

Where large size, configuration, or other structural constraints do not allow openings to be decked over (e.g. elevator shafts, stair wells, etc.), employees must be protected in accordance with the fall protection provisions of this standard. [29 CFR 1926.754(e)(2)(ii)]

Immediately and permanently be filled with the intended equipment or structure.

Or immediately be covered.

Covering Roof and Floor Openings:

Covers for roof and floor openings shall be capable of supporting, without failure, twice the weight of the employees, equipment, and materials that may be imposed on them at any one time. [29 CFR 1926.754(e)(3)(i)]

Workers Killed in Falls Through Decking Holes

Case Reports:

An employee fell from about the 60-foot level of a manufacturing facility where he was doing steel erection. He had just completed bolting up a vertical beam, and was attempting to disconnect the hoisting line, when he apparently backed into a floor opening in the metal decking on which he was standing. Guardrails had been manufactured for the opening but would not fit, and had been taken down to the ground for modification. The employee died of his injuries.

At around 10:00 a.m. on January 31, a steelworker was involved in metal decking installation. He fell approximately 20 feet through a roof opening to the ground floor, sustained multiple body injuries, and died the following day.

An employee for a steel erection company was helping to build an elevated automobile ramp. He was covering an opening on the ramp with metal decking when he fell about 42 feet through the opening and was killed. He was not using fall protection.

Workers Killed in Falls Through Decking Holes

Case Reports:

An employee fell from about the 60-foot level of a manufacturing facility where he was doing steel erection. He had just completed bolting up a vertical beam, and was attempting to disconnect the hoisting line, when he apparently backed into a floor opening in the metal decking on which he was standing. Guardrails had been manufactured for the opening but would not fit, and had been taken down to the ground for modification. The employee died of his injuries.

At around 10:00 a.m. on January 31, a steelworker was involved in metal decking installation. He fell approximately 20 feet through a roof opening to the ground floor, sustained multiple body injuries, and died the following day.

An employee for a steel erection company was helping to build an elevated automobile ramp. He was covering an opening on the ramp with metal decking when he fell about 42 feet through the opening and was killed. He was not using fall protection.

Unsecured Decking Causes Eighty-Foot Fall

Case Report:

While erecting a bridge, a worker placed metal decking onto the stringers of the bridge to be welded. When the first decking was placed, the employee apparently stepped onto that section in order to put down the next section. Because the decking he stepped onto was not secured in place, it slipped and the employee fell approximately 80 feet into the river.

Unsecured Decking Causes Eighty-Foot Fall

Case Report:

While erecting a bridge, a worker placed metal decking onto the stringers of the bridge to be welded. When the first decking was placed, the employee apparently stepped onto that section in order to put down the next section. Because the decking he stepped onto was not secured in place, it slipped and the employee fell approximately 80 feet into the river.

All columns must be evaluated by a competent person to determine whether guying or bracing is needed; if guying or bracing is needed,
it must be installed. [29 CFR 1926.755(a)(4)]

One Worker Killed, Three Injured as Columns Collapse

Case Report:

Four employees were sitting on steel roof beams. Two employees were bolting beams to columns and the other two employees were sitting on the beams connecting roof purlins. A gust of wind caused the columns to topple in a domino fashion. One of the employees connecting roof purlins fell 25 feet to his death, and the other three employees were hospitalized for injuries. Compliance with the new steel erection standard could have prevented this accident.

One Worker Killed, Three Injured as Columns Collapse

Case Report:

Four employees were sitting on steel roof beams. Two employees were bolting beams to columns and the other two employees were sitting on the beams connecting roof purlins. A gust of wind caused the columns to topple in a domino fashion. One of the employees connecting roof purlins fell 25 feet to his death, and the other three employees were hospitalized for injuries. Compliance with the new steel erection standard could have prevented this accident.

Inappropriate or inadequate connections of beams and columns is hazardous and can lead to collapses and worker fatalities. This section sets forth performance and specification requirements for connecting beams and columns, in order to minimize the hazard of structural collapse during the early stages of the steel erection process.

When two structural members on opposite sides of a column web, or a beam web over a column, are connected sharing common connection holes:

At least one bolt with its wrench-tight nut must remain connected to the first member; unless

A shop-attached, or field-attached seat or equivalentconnection device is supplied with the member in order to (See Appendix H to this subpart for examples of equivalent connection devices.) [29 CFR 1926.756(c)(1)]:

Secure the first member.

Prevent the column from being displaced.

If a seat or equivalent device is used:

The seat (or device) must be designed to support the load during the double connection process.

Before the nuts on the shared bolts are removed to make the double connection, it must be adequately bolted or welded to both [29 CFR 1926.756(c)(2)]:

Workers Hospitalized After Inadequately Secured Beams Fail

Case Reports:

Two employees were ordered by their foreman to take down a two-ton I-beam about 20 feet long, which they had themselves bolted to shear lugs the day before. The employees stood at opposite ends of the beam, one worker removing the bolts, while his co-worker released a strap, commonly known as a "come-along," that was supporting the other end of the beam. As the "come-along" was released, the shear lugs ripped from the column and the beam dropped, sending both workers to the floor 16 feet below. They were each hospitalized; one worker suffered injuries to his right foot that required surgery. Investigation showed that on the night prior to the accident, a welding crew was assigned to help relocate the beam to a different elevation. They started by securing the beam with the "come-along," then partially cut the beam's shear lugs. This was unknown to the workers the next day, because the foreman did not inspect the shear lugs, even though he admitted he saw the "come-along."

Three ironworkers were laying metal decking when the deck they were standing on let go from the support beam. The three workers fell some 13 feet, and were sent to the hospital with injuries. Investigation revealed that the support beam only had a single loose bolt at each connection, instead of two wrench-tight bolts as required by OSHA standards. The support beam rolled, and since the metal decking was not yet welded or secured to the beam, it slid off and carried the workers with it.

Workers Hospitalized After Inadequately Secured Beams Fail

Case Reports:

Two employees were ordered by their foreman to take down a two-ton I-beam about 20 feet long, which they had themselves bolted to shear lugs the day before. The employees stood at opposite ends of the beam, one worker removing the bolts, while his co-worker released a strap, commonly known as a "come-along," that was supporting the other end of the beam. As the "come-along" was released, the shear lugs ripped from the column and the beam dropped, sending both workers to the floor 16 feet below. They were each hospitalized; one worker suffered injuries to his right foot that required surgery. Investigation showed that on the night prior to the accident, a welding crew was assigned to help relocate the beam to a different elevation. They started by securing the beam with the "come-along," then partially cut the beam's shear lugs. This was unknown to the workers the next day, because the foreman did not inspect the shear lugs, even though he admitted he saw the "come-along."

Three ironworkers were laying metal decking when the deck they were standing on let go from the support beam. The three workers fell some 13 feet, and were sent to the hospital with injuries. Investigation revealed that the support beam only had a single loose bolt at each connection, instead of two wrench-tight bolts as required by OSHA standards. The support beam rolled, and since the metal decking was not yet welded or secured to the beam, it slid off and carried the workers with it.

Some of the most serious risks facing the ironworker are encountered during the erection of open web steel joists, particularly landing loads on unbridged joists and improperly placing loads on joists. Based on a recent analysis of OSHA data, more than half of ironworker fatalities due to collapse are related to the erection of steel joists.

Where steel joists are used and columns are not framed in at least two directions with solid web structural steel members, the columns must be made laterally stable during erection by field-bolting the steel joist at the column. (See exception below) [29 CFR 1926.757(a)(1)]

Unstable Columns Cause Joists to Collapse; One Dead, Three Injured

Case Reports:

Five ironworkers were distributing 90-foot-long open web bar joists on a building under construction. The bar joists were supported by vertical columns spaced 30 feet apart. The steel columns were not framed in at least two directions, and the bar joists were not field-bolted to the vertical columns to prevent collapse. The bar joists shifted, causing the vertical columns to lean. This resulted in the entire section of columns and open web bar joists to collapse. Two employees rode the iron down. One was killed and one received serious injuries.

Two employees had just finished setting and bolting a 60-foot steel truss atop two 30-foot steel columns. As the crane load line was disconnected, a high gust of wind blew over the truss and columns. One employee rode the truss to within approximately 12 feet of ground level when he fell off, striking his face and nose on the ground. The other employee rode the truss all the way to the ground and was thrown into the webbing when the truss bounced on impact. He suffered a sprained right ankle. The whole truss and column configuration then fell into another erected truss/column set, knocking it down as well. As allowed by the steel erection standards in place at the time, neither employee was tied off to a safety device.

Unstable Columns Cause Joists to Collapse; One Dead, Three Injured

Case Reports:

Five ironworkers were distributing 90-foot-long open web bar joists on a building under construction. The bar joists were supported by vertical columns spaced 30 feet apart. The steel columns were not framed in at least two directions, and the bar joists were not field-bolted to the vertical columns to prevent collapse. The bar joists shifted, causing the vertical columns to lean. This resulted in the entire section of columns and open web bar joists to collapse. Two employees rode the iron down. One was killed and one received serious injuries.

Two employees had just finished setting and bolting a 60-foot steel truss atop two 30-foot steel columns. As the crane load line was disconnected, a high gust of wind blew over the truss and columns. One employee rode the truss to within approximately 12 feet of ground level when he fell off, striking his face and nose on the ground. The other employee rode the truss all the way to the ground and was thrown into the webbing when the truss bounced on impact. He suffered a sprained right ankle. The whole truss and column configuration then fell into another erected truss/column set, knocking it down as well. As allowed by the steel erection standards in place at the time, neither employee was tied off to a safety device.

Shop-installed bridging clips, or functional equivalents, must be used where the bridging bolts to the steel joists. [29 CFR 1926.757(d)(6)(iii)]

When two pieces of bridging are attached to the steel joist by a common bolt, the nut that secures the first piece of bridging must not be removed from the bolt in order to attach the second. [29 CFR 1926.757(d)(6)(iv)]

Hoisting Cables Released Too Soon, Fatal Fall Results

Case Report:

An employee was sitting on a 40-foot-long bar joist, welded at one end, while he attempted to connect X-bracing to it at the other end. The hoisting cable was already released, and the joist was insufficiently bridged to support the load it was bearing. When it slipped, the employee rode the joist down 25 feet and died of massive head injuries.

Hoisting Cables Released Too Soon, Fatal Fall Results

Case Report:

An employee was sitting on a 40-foot-long bar joist, welded at one end, while he attempted to connect X-bracing to it at the other end. The hoisting cable was already released, and the joist was insufficiently bridged to support the load it was bearing. When it slipped, the employee rode the joist down 25 feet and died of massive head injuries.

During the construction period, the employer placing a load on steel joists must ensure that the load is distributed so as not to exceed the carrying capacity of any steel joist. [29 CFR 1926.757(e)(1)]

The edge of any construction load must be placed within 1 foot of the bearing surface of the joist end. [29 CFR 1926.757(e)(5)]

Overloaded Joists Fail, Fatal Fall Results

Case Report:

Two employees had unloaded two bundles of metal decking, two bundles of bridging and two bundles of roof frames onto six open web steel joists 25 above ground level. The joists were at 5½-foot centers, and welded on the end to the I-beam. The employees had just unhooked the second bundle of frames when one joist rolled, causing the employees to fall. All six joists broke from their welds and collapsed, landing on one of the employees. He died of his injuries. His co-worker was hospitalized but survived.

Decking Placed on Unsecured Joists Leads to Worker Injury

Case Report:

A bundle of 25 steel deck sheets was sitting on three open web joists, approximately 40 feet in length and about 25 feet above ground level. A worker was standing on the deck sheets as a second bundle was being landed on the other end of the same joists. The three joists rolled and collapsed, along with two additional joists. The worker began falling and attempted to jump away from the deck bundle, but his legs became entangled within the joist webbing. He landed on soft mud and sustained two broken legs. According to the project superintendent, none of the joists was secured or bridged at the time of load placement.

Overloaded Joists Fail, Fatal Fall Results

Case Report:

Two employees had unloaded two bundles of metal decking, two bundles of bridging and two bundles of roof frames onto six open web steel joists 25 above ground level. The joists were at 5½-foot centers, and welded on the end to the I-beam. The employees had just unhooked the second bundle of frames when one joist rolled, causing the employees to fall. All six joists broke from their welds and collapsed, landing on one of the employees. He died of his injuries. His co-worker was hospitalized but survived.

Decking Placed on Unsecured Joists Leads to Worker Injury

Case Report:

A bundle of 25 steel deck sheets was sitting on three open web joists, approximately 40 feet in length and about 25 feet above ground level. A worker was standing on the deck sheets as a second bundle was being landed on the other end of the same joists. The three joists rolled and collapsed, along with two additional joists. The worker began falling and attempted to jump away from the deck bundle, but his legs became entangled within the joist webbing. He landed on soft mud and sustained two broken legs. According to the project superintendent, none of the joists was secured or bridged at the time of load placement.

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